1. Field of the Invention
This invention relates to the field of gearshift mechanisms for use with automotive manual transmissions and more particularly pertains to such mechanisms that require substantial shifting effort by the vehicle operator when selecting reverse gear and to those that prevent engagement of reverse gear in certain circumstances.
2. Prior Art
German patent No. 30 03 079 describes a gearshift mechanism for a multiple speed manual transmission in which the fifth forward gear Position of the selector shaft is located in the same shift plane as the reverse gear position. The gearshift mechanism includes a lock that employs a spring-loaded rotatable locking cam to prevent shifting of the selector shaft from the fifth gear ratio position into the reverse gear position and force the selector shaft into the adjacent shift plane defined by other forward gear positions.
The gearshift mechanism described in that patent includes a spring-loaded locking cam rotatably mounted on a retaining pin inserted between two support plates. In that device it is necessary for the front surface of the locking cam to cooperate with a connection member located between the selector shaft and the gearshift lever. Rear stop surfaces cooperate with the corresponding surfaces on the retaining pin to limit rotational movement. This arrangement requires a large number of parts and the operating accuracy of the locking mechanism is substantially reduced by the accumulation of dimensional tolerances, which arise among the various components.
German application No. 20 62 691 describes a similar gearshift mechanism for a manual transmission in which a gearshift finger guides an internal gearshift plate provided on the selector shaft. The mechanism of this application makes no provision for preventing movement of the gear selector shaft from a forward gear position to the reverse gear position within a shift plane.